Dental crown



Oct} 16, 1928.

- J. PYETRY DENTAL CROWN Filed Dec. 8, 1925 4 sheets-sheet 1 FIG. 1

W %V/////AW///M7////,S v 1:1 am

INVENTOR J. PETRY DENTAL CROWN Oct. 16, 1928.

Filed Dec. 8, 1925 4 Sheets-Sheet 2 INVENTOR Oct. 16, 1928. 1,687,690

J. PETRY DENTAL CROWN Filed Dec. 8, 1925 4 Sheets-Sheet 3 \NVENTOR Oct. 16, 1928. v m 1,687,690

' J. PETRY DENTAL CROWN Filed DGC- 1925 Sheets-Sheet 4 I FIG.17

F|G.14 l I a llllllllllll 7l/II/Ii I FIG. 16 I, 90 95 94 89 92 i i 89 f /6 /6 A H G 92 88 9 .INVENTOR 9/ 77 I 'f I Patented Oct- 16, 1928.

UNITED STA,

JACOB PETBY, or PITTSBURGH, PENNS LVANIA,

DENTAL Application filed December My invention relates particularly to tooth crowns such as are employed in'dentistry. 5 i

My invention has for its object the pro-f vision of an improved apparatus for and a method of making tooth crowns,-wh'ereby a; better fitting crownis obtained, and one which is free from various imperfections heretofore commonly present therein.

Another object of my invention is to'sim-t plify and improve generallythe construction of and form of dental tooth crowns In makingthe tooth crowns itis desirable that the occlusal portion be provided with a chewingsurface that shall be of such" diam eter or width as to leave no space between it and adjacent teeth or crowns, inorder to present a substantially continuous chewing surface and to avoid the unsightly appearance which would result in cases where a Considerable space was present. Suchspaces not only result in collection of food particles and the breeding of germs, but the gum tissues at thosepoints will be irritated through pressure while masticating 'food, causing bleeding and receding of the gums, as'Well as unnecessary pain. 1 r The natural tooth at the gingival or gum line is ordinarily of smaller diameter than at its outer or occlusal end; Therefore, in order that a crown may fit properly, it is necessary that it tapers from its occlusal portion to its gingival opening. Crowns are commonly made lroinivhat might be termed cartridges of gold or other suitable metallic substance tliatare of substantially un form diameter from their closed ends to their'open ends. The problem then is to reduce the diameterthereof toward the open end, but diiliculty hasbeen experienced by reason of the fact: that in making such reduction in diameter objectionable irregularities, such as indr-znfcations, creases or fold-lines, and the like occur; In some cases the crown has been split for a port on of its'lcngzth and the edges of the split portion overlapped'and soldered in order to cause it'to closely embrace the tooth at the gingival line. In either instance, it is almost impossible to secure the desired closeness of fit between the crown and the tooth, so that destructive foreign matter finds its way'i'nto the space between the crown and the teeth and decay results, v

It has alsobeen customary to expand the occlusal endof the crowns somewhatfbut, by

caowiv. s, 1525. seriai'no; 74,203; v

the methods heretofore employed, such expans on oftenfresults in excessive thinningof the metalso that the finished crown isweakenedlto an objectionable degree and perhaps even torn when expanded,

In the manufacture of seamless crowns, it has been the custom to employ male and female the rnen'ibers of such 'form that the upper oropen end of the crown is of at least asgreat diameter as the lower or occlusal end thereof, andusually of slightly greater diameter, owing to "the necessity of removing the expanded'crown from a female die Inerriber. This is directly the opposite of the shape desiredthat is, in the completed form the crown should bewider' at its base, and relatively narrow at its open or gin ival end, By employing the dies shown in t e aCcornpanying drawing it is possible 'toform a crown with a relatively "large lowerfend, inga mold "or die havingonly two movable parts, and nevertheless perin tconvenientre inoval' of the crown distortion/ v p In the accompanying. drawing I have shown some ofthe waysin'which my invejn -f tion may be practiced. Fig; 1 is ascheniatie view showing V the manner in p which] the crown blanl:v may be [passed through fth e' early stages of fo1'mation; Fig. 2 is a view showing the inanner :in which a blank' is o ocrat d upon by the o'cclusal forming die I; Fig. '3 is a vertical sectional yiewj e blank, removed from the die of Fig.

I 4 is a planlview thereof; Figfl 5 is icw showing" one manner in which the from the dies Without,

rion of the blank; Fig. 9 is a transverse sectional vi ew ofa portion of the apparatus of Fig. 9; 10 is a view of'aportion of the apparatus of Fig. 8, but showing the a plunger head. in operativ'e'position with re-. spcct to a blankcarriedby the dies; Fig l1 is a plan view of the dies ofFigf. 8 l2 is a view showing the form of the tooth crown after it has been operated uponby the plunger head and dies of Fig; 8; 1.3 is a vieW'shQ ingthe blank of Fig. 12

'7 trimmed and ready for use by the dentist,

E ig His" an elevational sectional viewof reduced indiameter; Fig. 6 is a sectional modified form of apparatus for forming crowns; Fig. l5 fis a sectional plan view,.on

an enlarged scale, taken on the line 15 -15 of Fig. 14; Fig. 16 is an elevational sectional view taken on the line 1616 of Fig.'-

15; Fig. 17 is a sectional view, on an enlarged scale, of a portion of the apparatus ReferringtoFigs. 1 and2 of the drawing,

I show a die block or plate 20 that is proplungers 21, 22, 23 and 24 cooperate. The

plungers are shown as mounted on a vertically reciprocable head 25 that may be opera-ted in any desired manner, to move the vplunger into holes in the plate 20.

In making tooth crowns, a disc'26 of gold or othersuitable metal isplaced in the position shown, and the plunger head 25 brought down to depress said disc. The partially formed cartridge is then moved into the next smaller'hole andits diameter reduced by the plunger 22.,In the drawing I have shown four plungers of progressively smaller diameter, but a greater or lessnum-. ber maybe provided, depending upon the, size. and character of the crown to be formed. ,The plungers are .all preferably oval. in cross, section and the lower or occlusal end of the blank has its greatest diameter substantially equal tothe greatest diameter of the finished crown, sothat excessive expansion of the lower or closed end.

of the cartridge in order to form the usual enlarged; occlusal surface, with consequent thinning of the metal, is avoided.

After the crown has been operated upon by-the plunger 24 it isplaced in a die 27 that is provided with depressions 28' which have the general form of the occlusal surface desired for the crown. A plunger'29 is provided with complementary surfaces and is brought into engagement with the crown, as shown more clearly in Fig. 2.

Thecrown 26 is then of thewform shown in Figs. 3 and 4.

vided. Thedie hasv a tapering mouth or opening 31 into which the open endof'the crown 26 may be gradually inserted, the. crown and the die meanwhile being given.

relative: rotative movement through any suitable means. The crown, after be ng "block 36 is locked in operated uponby the die-30, is in the form shownm Figs. 6 and 7, SllClIVlBWS, however, belng on an enlarged scale.

The next step in the formation of the crown consists. in placing it in the die and subjecting the same to hydraulic pressure sufiicient to expand the metal of the crown and in orderto bring it to the desired contourand smoothness. This eXpansionis accomplished by means of apparatus shown in .Figs. 8 to 11, inclusive.

In these views I provide a base 32 to which is rigidly conposed die 34. The die 33 is movably held in place by'a set screw 35lwhich permits convenient substitution of dies 33 of various sizes and forms. I The lateral die 34 is supported by arblock 36 which has dove-tail v connection with a plate 37 and is adjustable horizontally by means of adjusting screws 38'(Fig. 11). The lateral'die 34 may also bereadily replaced, since it is secured to the block 36'by screws39. The set screws .38

.operate through a'block 40. that is secured to the base of the dies structure and the die set screws 41. V Asecond lateral die .42 is provided, such die being bolted to the block 43 that has dove-tail connection with the members 37. This die, asin the case ofv the dies 33 and 34 may be readily replaced by a die of other means of screws 44. I

j The members 37 are secured to a plate 45 position by means of form, since itis attached to the block 43 by n'ected abottom die 33 and a laterally disvided with a number of holes with which low which is in turn supported by the base 32.

A pivot pin 46 extends upwardly from the plate 45 and a pivot pin 47 is carried by the block 43. Toggle links 48 and 49 are joined to the pivots 46 and 47, respectively, and are "pivotally connected to one another at 50. A handle 51 is secured tothe link 48. When the handle 51 is swung ab out'the pivot 46 as an axis, the link 48 will'be actuated to move the link 49 and shift the block 43 laterally.

The hydraulic plunger apparatus which cooperates with the dies just described, comprises a plunger 53 that has a longitudinal passage and a nozzle 54 communicating with said passage. A collar 55has screw threaded engagement wlth the bottom of the plunger and is adjustably longitudinally thereof to adapt it to metals of'difierent thicknesses or to dies of differentdimensions.

The plunger 53 isenlarged atitsupper en'dto form a piston-like portion 56 that reciprocates in a cylindrical casing 57, the plunger being normally held in its lowermost position by a-compression-spring 58 interposed between the upper end of the cylinder 57 and the plunger 53. The cylinder 57 1s carriedin a head block 59 that is reclproeated vertically in any desired manner in order to bring the lower end of the respect to the dies therebeneath.

, wardly opening check valve-'62 with a pas A reservoir is provided for containing oil or anyother suitable fluid and coinmunicates through a passage 61 and an insage 63 in the wallof the cylinder 57, the

passage 63 extends for some distance cir cumferentially of said Wall and has communication with a plurality of vertically extending passages 6a which are formed in the wall of the cylinder 57 The passages 64, in turn communicate with an annular passage 65 in the underside of the cylinder head 66. The cylinder head is provided with a. plurality of passages 67 that coinniunicate at their upper ends with the interior of the cylinder. 57. c I

' An'exhaust pipe 68 has communication, through an outwardly opening check valve 69 with a vertical passage 'TOformed in the wall of the cylinder. The vertical passage 70 communicates with the interior of the cylinder through a passage 71, formed in the cylinder head 66;

lVhen a crown 26 has beenpassed'through the stages shown in'Figs. 1 to 7 inclusive,

itis placed inthe dies 33, 34 and 42in a manner as shown in Fig. 8. Theoil from the reservolr 60 has been previously drawn into the cylinder 57=by moving the piston 56 and plunger 53 carried thereby to their extreme upper position against compression of the spring 58 and then permittiiigsuch piston to descend underthe action of the spring, thus drawing in-a charge ofwoil from the reservoir; WVith a crown inplace able distance. This escap'eis elfected through" in the die and a charge of oil present. in the cylinder; the head 59 is lower'ed to bring the lower end of the plunger 53 into engagementwit-h the upper edg'e of the crown As such lowering movement continues, the lower end of the plunger, by reason of its conical form, expands the upper end of the crown 26 in the manner shown in Fig. 10. The crown being of relatively soft'metal, a tight seal is thereby provided which prevents the escape of the oilthat forced through the plunger into the crown, bycontinned downward movement of the head 59. The fluid isplaced under suflicientlywhigh pressure to expand the. cartridges so much as may be necessary to completely fill the dies. The lower face of the collar 55 in ay be provided withja seating surface that" inder 57 is in excess of the amount required and itis desirable that provision therefore be made to permitthe escape thereof when the head 59 is forced downward a consider the conduits 71 and 70 and-the check valve 69, to the drain pipe 68 from whence it may be'returned to the reservoir 60. As the check valve 62 opens inwardly toward the cylinder, oil will be. drawn from the reservoir upon downward movement of thepiston but.

will be prevented from flowing back into the reservoir upon; upward movement of the piston. On the other hand thevalve 69 opens outwardly so i. that: air will not be drawn: into the cyl'nder to the exclusion of oil from the reservoir and to permit the expulsion of sur-.

plus oil, as above explained. I

When the crown has been operated on,: as sli'ouniirn Fig. 10, the plunger, 53'is retracted and thev handle 51 turned to slide the die block 413th inoperativeposition. The crown, may then be readily removed wrtlmu-tanow ingthe dies 83-a-nd34. I believe'this manner of i'orni ng an article with an enlarged inner end, between two lateral and one bottom die of such form that thearticle can be removed from the dies simply by removing one of the lateral dies, is new.

lVhen the crown has been removed the finishing" dies it is of the form shown-in Fig. 12. The final operation consists in cutting olf: theflared upper end of the crown,

thereby bringing it tothe formtasshown in Fig. 10.

lnFigs. 14 to 19,-inclusive, I-have shown from a-m-odified form of apparatus by which den; i

stalcrowns similar to those show 'n-inlFig; V 13 may be formed; This latter form of apshown comprises uprights 76, t'o'the top of which is secured a block 77 abovewlnch eX- tend guide posts 78 upon which is mounted: a head block'79;thatrhas screw threaded engagement with a screw shaft '80 which is provided with a handle 81 The screw shaft 80 is connected-ton cross head 82 whichis movable vertically along theguidepOst-s 78".!

The cross head 82 carries a chuck 85-3 cf any desired form, for holdingplungendies to beJ herenaftcr "described; a

A' stud plate 84 is provided with :diametrh cally disposed recesses, the wallsot which partially embrace the pOsts TS, sothat'iit will be non rota'table with respect toth e posts. The plate 814: is removable when the-crosshead 82 has been raised sufficient distance-to 886's mounted within the gear case and.

"the studs 92 being permit the plate 8 L to be tilted so that the edges thereof will clear the inner sides of the posts 78. 9

An annular gear case member 85 is mount- ,ed upon the bloclr77 and is held in place thereon by the lower ends of the guide posts 78. The member 85 1s recessed'tortne ro ception of a worm 86 and s provided with suitable bushings for a shaft 87 by means or which said worm is operated. A worm gear meshes wlth the worm 86. w 'lhe block 8a. is provided with two pairs ot studs 89 and and the worm gear 88 is provided with two pairs of studs '91. and 92, longer than are the studs 91.

Three pairs of raoi ally movable die plates; 98, 9a and are provided, resting upon'the worm gear 88. Each die plate is provided at one end with acircular opening that closely contact with the studs.

engaged by the upper ends or" the studs91, -while'the studs 90 pass through the slotted said plates. Similarly the up openings in the studs 92 have close-fitting per ends of engagement downwardly extending studs pass loosely through the slotsin theplates 95; the lower extremities of the studs-89 closely engageholes in the plates 93,- and the studs 92, in-

termediate their ends, pass through theslots intheplates 93.

The studs 89 and 90 are rigidly supported in the plate 84 and therefore are held against movement about the axis of the gear wheel 88. The studs 91 and 92 are rigidly secured to the gear wheel 88 and are therefore rotatable therewith. It will be seen therefore that if the worm 86 be so turned as to rotate the gear wheel 88, in a counter clock-wise direction, as viewed in Fig.2, the studs 91 and 92 of the gear wheel will each be so moved as to carry one end oft-he plates 95 antl 9 l, respectively, toward the Vertical and horizontal diametrie lines, respectively, of. the gear wheel (Fig. 2), the oppositeend of 5' each plate being held against movement by thus reducing the openings between said;

means of the studs 90 and 89, respectively,

that are ca "ried by the fixed plate 84. I The.

mid portions of such plates will therefore be moved toward the axis of the gear wheel 88,

plates The plates 98' will be similarly moved,by reason of their engagement with the studs 89 and 92.

Each of the plates at with the; upper plates 95; the

a curved recess, although the curvature of,

the recesses in theplatcs 95 and93 are more oval than'are the recesses in the plates 94. When the gear wheel 88 is movedin a clockwise direction(Fig. 2), the mid portions of the die plates. will of course move radially outward, to enlarge. the'spaces between the pairs ofplatea The chuck support the plunger. dies '90 and 97 while a dieblock 98'supportsa bottom die 99. The

block 98 is supported by means of springs 100 which are compressed by a vertically slidableplate 101 that. may beheld in elevated position in any desired manner, and which will fall-upon cushioning springs 102 .when released, l'aerinitting thedie block 98 LO iall. I v v v In the operation of the dev1ce,a crown blank or cartridge, usually otunitorm di;

ameter andclosed at one'end, is provided and is mounted upon the bottom Cll8'99 'as shown in Fig. '14- whereupon the screw 80' to which the plunger die 96iS, secured is moved down, forcing sa d plunger die into the cartridge, which is'represented by the adapted to detachably,

letter A, to press the bottom'oi: occlusal por'-- tion thereof tothe" desired form, which in the present case is represented'byntwo curved lines." lhe die 96 is thenwithdrawn and an other die or mandrel 97 inserted in; the chuck 83.. The die 97, particularly atvits lower end,

is or" smaller cross sectionthanis the lower end ofithe die 96.; Therefore wax. or other suitable material103 is introduced into the partially formed crown A to prevent distortion of the previously formed occlusal 1 portion. The, die 97 is then caused to move downwardlyby turning thehandle8l and.

at the same time the shaft. 87 is rotated slowly in order to gradually drawinthe lateral dies 93, 94 and 95. 'By reason of the simultaneous movements just referred to, the upper portion of the crown is-gradually shrunk around the mandrel or die 97, as will appear more clearly in Figsol'and 5. The mandrel97 nay be OVilllIl cross sectionas shown in Fig. 2, or may be of other cross sectional form, depend'ng upon the shape of the particular tooth is desired. I

The mandrel 97 may be replaced by another'mandrel of still smaller cross sectional area, in order to effect still further reduction oi the gingival po-rtionof the for which the crown crown. WVhile the desired reduction in. diameter o't the crown may in some cases be ellected by the employmentof but a,

single mandrel 97, two orjmore successively smaller .mandrels may be required, particularly where considerable reduction n diameter of the crown is desired, since a too great, reduction in diaineteron a singlecpass,

., j may result intolds or dent sin' the crown. its inner edge has After each pass of reducing mandrel manner.

the crown ismoved up slightly by pressure of the springs 100, the lateral dies being retracted slightly,.if necessary, to permit such movement. Upon the nextdrawing' operation the crown is given another longitudinal downward movement, simultaneously with another inward movement of the lateral dies.

After completion of the drawing operation, the wax may be removed by heat, chipplng it out, by acid, or in any other desired It will be apparent that the process may be performed by various other means than that shown in'the drawing, and that it may vbe employed Y in other arts thanthat of dentistry.

I claim as my invention:

1. Die structure for forming cartridgedike members having their closed ends oft greater diameter than their open ends, comprising a bottom die member, a lateral die member vnormally fixed relative to said bottom die member, and'a second lateral 'die member a movable with respect to the other members. 1

2. Die structure. for forming cartridgellke members having thelr closed ends of diameter than their open ends, comprising abottom die member, a lateral die member normally fixed relative to said bottom die member, and a second lateral diemember movable with respect to the other members, the said lateraldle members havlng undercut portions.

4. Die structure for forming cartridge-like members having their closed ends of greater diameter than their open ends, comprising a bottom die member, and two lateral die members, one of which ismovable relative to the other members and one of the lateral die members: being undercut. In testimony whereofl, the said JACOB PETRY, have hereunto set my hand.

JACOB PETRY. 

